Question 18
Let $a_1, a_2, \dots, a_{2011}$ be nonnegative reals with sum $\frac{2011}{2}$. Prove that
$$
\left| \prod_{cyc} (a_n - a_{n+1}) \right| = \left| (a_1 - a_2)(a_2 - a_3) \dots (a_{2011} - a_1) \right| \le \frac{3\sqrt{3}}{16}.
$$
$$
\left| \prod_{cyc} (a_n - a_{n+1}) \right| = \left| (a_1 - a_2)(a_2 - a_3) \dots (a_{2011} - a_1) \right| \le \frac{3\sqrt{3}}{16}.
$$